It's been a couple of years and a couple of million dollars. Finally, researchers and graduate students who have spent years developing intelligent water sensors released them into the Sacramento River on Wednesday, about 80 miles east of San Francisco.

That area of the river is a mixture of salt water from the nearby San Francisco Bay area. Altogether, the water within the Delta region supplies two-thirds of California's drinking water.

Researchers hope that their sensors will be able to help track environmental spills and the flow of water, which could also help improve salmon spawning.

"This is the way of the future," said Alexandre Bayen, associate professor at the University of California, Berkeley who is supervising the project, called the Floating Sensor Network. "We're moving from an age when humans were deploying things and baby-sitting them to an age where you just put the robots in the water, they do their job, they come back or they call you if they have a problem."

Some of the sensors are equipped with Android smart phones inside their waterproof cases. A few of them auto-post to Twitter whenever they are in use. Check @fsnandroid61.

Researchers from University of California, Berkeley, San Francisco State University, The Center for Information Technology Research in the Interest of Society and the Lawrence Berkeley National Laboratory helped with the project.